/* gzio.c -- IO on .gz files
 * Copyright (C) 1995-2002 Jean-loup Gailly.
 * For conditions of distribution and use, see copyright notice in zlib.h
 *
 * Compile this file with -DNO_DEFLATE to avoid the compression code.
 */

/* memgzio.c - IO on .gz files in memory
 * Adapted from original gzio.c from zlib library by Forgotten
 */

/* @(#) $Id$ */

#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "memgzio.h"

#ifndef local
#define local static
#endif

#ifndef DEF_MEM_LEVEL
#define DEF_MEM_LEVEL 8
#endif

#ifndef OS_CODE
#define OS_CODE 3
#endif

#ifndef zmemcpy
#define zmemcpy memcpy
#endif

/*struct internal_state {int dummy;};*/ /* for buggy compilers */

#ifndef Z_BUFSIZE
#ifdef MAXSEG_64K
#define Z_BUFSIZE 4096 /* minimize memory usage for 16-bit DOS */
#else
#define Z_BUFSIZE 16384
#endif
#endif
#ifndef Z_PRINTF_BUFSIZE
#define Z_PRINTF_BUFSIZE 4096
#endif

#define ALLOC(size) malloc(size)
#define TRYFREE(p)                                                                                 \
        {                                                                                          \
                if (p)                                                                             \
                        free(p);                                                                   \
        }

static int gz_magic[2] = { 0x1f, 0x8b }; /* gzip magic header */

/* gzip flag byte */
#define ASCII_FLAG 0x01  /* bit 0 set: file probably ascii text */
#define HEAD_CRC 0x02    /* bit 1 set: header CRC present */
#define EXTRA_FIELD 0x04 /* bit 2 set: extra field present */
#define ORIG_NAME 0x08   /* bit 3 set: original file name present */
#define COMMENT 0x10     /* bit 4 set: file comment present */
#define RESERVED 0xE0    /* bits 5..7: reserved */

typedef struct _MemFile {
        char *memory;
        char *next;
        int available;
        int error;
        char mode;
} MEMFILE;

typedef struct mem_stream {
        z_stream stream;
        int z_err;       /* error code for last stream operation */
        int z_eof;       /* set if end of input file */
        MEMFILE *file;   /* memoru file */
        Byte *inbuf;     /* input buffer */
        Byte *outbuf;    /* output buffer */
        uLong crc;       /* crc32 of uncompressed data */
        char *msg;       /* error message */
        int transparent; /* 1 if input file is not a .gz file */
        char mode;       /* 'w' or 'r' */
        long startpos;   /* start of compressed data in file (header skipped) */
} mem_stream;

local gzFile gz_open OF((char *memory, const int available, const char *mode));
local int do_flush OF((gzFile file, int flush));
local int get_byte OF((mem_stream * s));
local void check_header OF((mem_stream * s));
local int destroy OF((mem_stream * s));
local void putLong OF((MEMFILE * file, uLong x));
local uLong getLong OF((mem_stream * s));

local MEMFILE *memOpen(char *memory, int available, char mode)
{
        MEMFILE *f;

        if (available <= 8)
                return NULL;

        if (mode != 'w' && mode != 'r')
                return NULL;

        f = (MEMFILE *)malloc(sizeof(MEMFILE));

        f->memory = memory;
        f->mode = mode;
        f->error = 0;

        if (mode == 'w') {
                f->available = available - 8;
                f->next = memory + 8;
                memory[0] = 'V';
                memory[1] = 'B';
                memory[2] = 'A';
                memory[3] = ' ';
                *((int *)(memory + 4)) = 0;
        } else {
                if (memory[0] != 'V' || memory[1] != 'B' || memory[2] != 'A' || memory[3] != ' ') {
                        free(f);
                        return NULL;
                }
                f->available = *((int *)(memory + 4));
                f->next = memory + 8;
        }

        return f;
}

local size_t memWrite(const void *buffer, size_t size, size_t count, MEMFILE *file)
{
        size_t total = size * count;

        if (file->mode != 'w') {
                file->error = 1;
                return 0;
        }

        if (total > (size_t)file->available) {
                total = file->available;
        }
        memcpy(file->next, buffer, total);
        file->available -= (int)total;
        file->next += total;
        return total;
}

local size_t memRead(void *buffer, size_t size, size_t count, MEMFILE *file)
{
        size_t total = size * count;

        if (file->mode != 'r') {
                file->error = 1;
                return 0;
        }

        if (file->available == 0)
                return -1;

        if (total > (size_t)file->available) {
                total = file->available;
        }
        memcpy(buffer, file->next, total);
        file->available -= (int)total;
        file->next += total;
        return total;
}

local int memPutc(int c, MEMFILE *file)
{
        if (file->mode != 'w') {
                file->error = 1;
                return -1;
        }

        if (file->available >= 1) {
                *file->next++ = c;
                file->available--;
        } else
                return -1;

        return c;
}

local long memTell(MEMFILE *f)
{
        return (long)(f->next - f->memory) - 8;
}

local int memError(MEMFILE *f)
{
        return f->error;
}

local int memClose(MEMFILE *f)
{
        if (f->mode == 'w') {
                *((int *)(f->memory + 4)) = memTell(f);
        }
        free(f);
        return 0;
}

local int memPrintf(MEMFILE *f, const char *format, ...)
{
        char buffer[80];
        va_list list;
        int len;

        va_start(list, format);
        len = vsprintf(buffer, format, list);
        va_end(list);

        return (int)memWrite(buffer, 1, len, f);
}

/* ===========================================================================
     Opens a gzip (.gz) file for reading or writing. The mode parameter
   is as in fopen ("rb" or "wb"). The file is given either by file descriptor
   or path name (if fd == -1).
     gz_open return NULL if the file could not be opened or if there was
   insufficient memory to allocate the (de)compression state; errno
   can be checked to distinguish the two cases (if errno is zero, the
   zlib error is Z_MEM_ERROR).
*/
local gzFile gz_open(memory, available, mode) char *memory;
const int available;
const char *mode;
{
        int err;
        int level = Z_DEFAULT_COMPRESSION; /* compression level */
        int strategy = Z_DEFAULT_STRATEGY; /* compression strategy */
        char *p = (char *)mode;
        mem_stream *s;
        char fmode[80]; /* copy of mode, without the compression level */
        char *m = fmode;

        s = (mem_stream *)ALLOC(sizeof(mem_stream));
        if (!s)
                return Z_NULL;

        s->stream.zalloc = (alloc_func)0;
        s->stream.zfree = (free_func)0;
        s->stream.opaque = (voidpf)0;
        s->stream.next_in = s->inbuf = Z_NULL;
        s->stream.next_out = s->outbuf = Z_NULL;
        s->stream.avail_in = s->stream.avail_out = 0;
        s->z_err = Z_OK;
        s->z_eof = 0;
        s->crc = crc32(0L, Z_NULL, 0);
        s->msg = NULL;
        s->transparent = 0;
        s->file = NULL;

        s->mode = '\0';
        do {
                if (*p == 'r')
                        s->mode = 'r';
                if (*p == 'w' || *p == 'a')
                        s->mode = 'w';
                if (*p >= '0' && *p <= '9') {
                        level = *p - '0';
                } else if (*p == 'f') {
                        strategy = Z_FILTERED;
                } else if (*p == 'h') {
                        strategy = Z_HUFFMAN_ONLY;
                } else {
                        *m++ = *p; /* copy the mode */
                }
        } while (*p++ && m != fmode + sizeof(fmode));
        if (s->mode == '\0')
                return destroy(s), (gzFile)Z_NULL;

        if (s->mode == 'w') {
#ifdef NO_DEFLATE
                err = Z_STREAM_ERROR;
#else
                err = deflateInit2(&(s->stream),
                                   level,
                                   Z_DEFLATED,
                                   -MAX_WBITS,
                                   DEF_MEM_LEVEL,
                                   strategy);
                /* windowBits is passed < 0 to suppress zlib header */

                s->stream.next_out = s->outbuf = (Byte *)ALLOC(Z_BUFSIZE);
#endif
                if (err != Z_OK || s->outbuf == Z_NULL) {
                        return destroy(s), (gzFile)Z_NULL;
                }
        } else {
                s->stream.next_in = s->inbuf = (Byte *)ALLOC(Z_BUFSIZE);

                err = inflateInit2(&(s->stream), -MAX_WBITS);
                /* windowBits is passed < 0 to tell that there is no zlib header.
                 * Note that in this case inflate *requires* an extra "dummy" byte
                 * after the compressed stream in order to complete decompression and
                 * return Z_STREAM_END. Here the gzip CRC32 ensures that 4 bytes are
                 * present after the compressed stream.
                 */
                if (err != Z_OK || s->inbuf == Z_NULL) {
                        return destroy(s), (gzFile)Z_NULL;
                }
        }
        s->stream.avail_out = Z_BUFSIZE;

        errno = 0;
        s->file = memOpen(memory, available, s->mode);

        if (s->file == NULL) {
                return destroy(s), (gzFile)Z_NULL;
        }

        if (s->mode == 'w') {
                /* Write a very simple .gz header:
                 */
                memPrintf(s->file,
                          "%c%c%c%c%c%c%c%c%c%c",
                          gz_magic[0],
                          gz_magic[1],
                          Z_DEFLATED,
                          0 /*flags*/,
                          0,
                          0,
                          0,
                          0 /*time*/,
                          0 /*xflags*/,
                          OS_CODE);
                s->startpos = 10L;
                /* We use 10L instead of ftell(s->file) to because ftell causes an
                 * fflush on some systems. This version of the library doesn't use
                 * startpos anyway in write mode, so this initialization is not
                 * necessary.
                 */
        } else {
                check_header(s); /* skip the .gz header */
                s->startpos = (memTell(s->file) - s->stream.avail_in);
        }

        return (gzFile)s;
}

/* ===========================================================================
     Opens a gzip (.gz) file for reading or writing.
*/
gzFile ZEXPORT memgzopen(memory, available, mode) char *memory;
int available;
const char *mode;
{
        return gz_open(memory, available, mode);
}

/* ===========================================================================
     Read a byte from a mem_stream; update next_in and avail_in. Return EOF
   for end of file.
   IN assertion: the stream s has been sucessfully opened for reading.
*/
local int get_byte(s) mem_stream *s;
{
        if (s->z_eof)
                return EOF;
        if (s->stream.avail_in == 0) {
                errno = 0;
                s->stream.avail_in = (uInt)memRead(s->inbuf, 1, Z_BUFSIZE, s->file);
                if (s->stream.avail_in == 0) {
                        s->z_eof = 1;
                        if (memError(s->file))
                                s->z_err = Z_ERRNO;
                        return EOF;
                }
                s->stream.next_in = s->inbuf;
        }
        s->stream.avail_in--;
        return *(s->stream.next_in)++;
}

/* ===========================================================================
      Check the gzip header of a mem_stream opened for reading. Set the stream
    mode to transparent if the gzip magic header is not present; set s->err
    to Z_DATA_ERROR if the magic header is present but the rest of the header
    is incorrect.
    IN assertion: the stream s has already been created sucessfully;
       s->stream.avail_in is zero for the first time, but may be non-zero
       for concatenated .gz files.
*/
local void check_header(s) mem_stream *s;
{
        int method; /* method byte */
        int flags;  /* flags byte */
        uInt len;
        int c;

        /* Check the gzip magic header */
        for (len = 0; len < 2; len++) {
                c = get_byte(s);
                if (c != gz_magic[len]) {
                        if (len != 0)
                                s->stream.avail_in++, s->stream.next_in--;
                        if (c != EOF) {
                                s->stream.avail_in++, s->stream.next_in--;
                                s->transparent = 1;
                        }
                        s->z_err = s->stream.avail_in != 0 ? Z_OK : Z_STREAM_END;
                        return;
                }
        }
        method = get_byte(s);
        flags = get_byte(s);
        if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
                s->z_err = Z_DATA_ERROR;
                return;
        }

        /* Discard time, xflags and OS code: */
        for (len = 0; len < 6; len++)
                (void)get_byte(s);

        if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
                len = (uInt)get_byte(s);
                len += ((uInt)get_byte(s)) << 8;
                /* len is garbage if EOF but the loop below will quit anyway */
                while (len-- != 0 && get_byte(s) != EOF)
                        ;
        }
        if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
                while ((c = get_byte(s)) != 0 && c != EOF)
                        ;
        }
        if ((flags & COMMENT) != 0) { /* skip the .gz file comment */
                while ((c = get_byte(s)) != 0 && c != EOF)
                        ;
        }
        if ((flags & HEAD_CRC) != 0) { /* skip the header crc */
                for (len = 0; len < 2; len++)
                        (void)get_byte(s);
        }
        s->z_err = s->z_eof ? Z_DATA_ERROR : Z_OK;
}

/* ===========================================================================
* Cleanup then free the given mem_stream. Return a zlib error code.
  Try freeing in the reverse order of allocations.
*/
local int destroy(s) mem_stream *s;
{
        int err = Z_OK;

        if (!s)
                return Z_STREAM_ERROR;

        TRYFREE(s->msg);

        if (s->stream.state != NULL) {
                if (s->mode == 'w') {
#ifdef NO_DEFLATE
                        err = Z_STREAM_ERROR;
#else
                        err = deflateEnd(&(s->stream));
#endif
                } else if (s->mode == 'r') {
                        err = inflateEnd(&(s->stream));
                }
        }
        if (s->file != NULL && memClose(s->file)) {
#ifdef ESPIPE
                if (errno != ESPIPE) /* fclose is broken for pipes in HP/UX */
#endif
                        err = Z_ERRNO;
        }
        if (s->z_err < 0)
                err = s->z_err;

        TRYFREE(s->inbuf);
        TRYFREE(s->outbuf);
        TRYFREE(s);
        return err;
}

/* ===========================================================================
     Reads the given number of uncompressed bytes from the compressed file.
   gzread returns the number of bytes actually read (0 for end of file).
*/
int ZEXPORT memgzread(file, buf, len) gzFile file;
voidp buf;
unsigned len;
{
        mem_stream *s = (mem_stream *)file;
        Bytef *start = (Bytef *)buf; /* starting point for crc computation */
        Byte *next_out;              /* == stream.next_out but not forced far (for MSDOS) */

        if (s == NULL || s->mode != 'r')
                return Z_STREAM_ERROR;

        if (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO)
                return -1;
        if (s->z_err == Z_STREAM_END)
                return 0; /* EOF */

        next_out = (Byte *)buf;
        s->stream.next_out = (Bytef *)buf;
        s->stream.avail_out = len;

        while (s->stream.avail_out != 0) {
                if (s->transparent) {
                        /* Copy first the lookahead bytes: */
                        uInt n = s->stream.avail_in;
                        if (n > s->stream.avail_out)
                                n = s->stream.avail_out;
                        if (n > 0) {
                                zmemcpy(s->stream.next_out, s->stream.next_in, n);
                                next_out += n;
                                s->stream.next_out = next_out;
                                s->stream.next_in += n;
                                s->stream.avail_out -= n;
                                s->stream.avail_in -= n;
                        }
                        if (s->stream.avail_out > 0) {
                                s->stream.avail_out -=
                                    (uInt)memRead(next_out, 1, s->stream.avail_out, s->file);
                        }
                        len -= s->stream.avail_out;
                        s->stream.total_in += (uLong)len;
                        s->stream.total_out += (uLong)len;
                        if (len == 0)
                                s->z_eof = 1;
                        return (int)len;
                }
                if (s->stream.avail_in == 0 && !s->z_eof) {
                        errno = 0;
                        s->stream.avail_in = (uInt)memRead(s->inbuf, 1, Z_BUFSIZE, s->file);
                        if (s->stream.avail_in == 0) {
                                s->z_eof = 1;
                                if (memError(s->file)) {
                                        s->z_err = Z_ERRNO;
                                        break;
                                }
                        }
                        s->stream.next_in = s->inbuf;
                }
                s->z_err = inflate(&(s->stream), Z_NO_FLUSH);

                if (s->z_err == Z_STREAM_END) {
                        /* Check CRC and original size */
                        s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));
                        start = s->stream.next_out;

                        if (getLong(s) != s->crc) {
                                s->z_err = Z_DATA_ERROR;
                        } else {
                                (void)getLong(s);
                                /* The uncompressed length returned by above getlong() may
                                 * be different from s->stream.total_out) in case of
                                 * concatenated .gz files. Check for such files:
                                 */
                                check_header(s);
                                if (s->z_err == Z_OK) {
                                        uLong total_in = s->stream.total_in;
                                        uLong total_out = s->stream.total_out;

                                        inflateReset(&(s->stream));
                                        s->stream.total_in = total_in;
                                        s->stream.total_out = total_out;
                                        s->crc = crc32(0L, Z_NULL, 0);
                                }
                        }
                }
                if (s->z_err != Z_OK || s->z_eof)
                        break;
        }
        s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));

        return (int)(len - s->stream.avail_out);
}

#ifndef NO_DEFLATE
/* ===========================================================================
     Writes the given number of uncompressed bytes into the compressed file.
   gzwrite returns the number of bytes actually written (0 in case of error).
*/
int ZEXPORT memgzwrite(file, buf, len) gzFile file;
const voidp buf;
unsigned len;
{
        mem_stream *s = (mem_stream *)file;

        if (s == NULL || s->mode != 'w')
                return Z_STREAM_ERROR;

        s->stream.next_in = (Bytef *)buf;
        s->stream.avail_in = len;

        while (s->stream.avail_in != 0) {
                if (s->stream.avail_out == 0) {
                        s->stream.next_out = s->outbuf;
                        if (memWrite(s->outbuf, 1, Z_BUFSIZE, s->file) != Z_BUFSIZE) {
                                s->z_err = Z_ERRNO;
                                break;
                        }
                        s->stream.avail_out = Z_BUFSIZE;
                }
                s->z_err = deflate(&(s->stream), Z_NO_FLUSH);
                if (s->z_err != Z_OK)
                        break;
        }
        s->crc = crc32(s->crc, (const Bytef *)buf, len);

        return (int)(len - s->stream.avail_in);
}
#endif
/* ===========================================================================
     Flushes all pending output into the compressed file. The parameter
   flush is as in the deflate() function.
*/
local int do_flush(file, flush) gzFile file;
int flush;
{
        uInt len;
        int done = 0;
        mem_stream *s = (mem_stream *)file;

        if (s == NULL || s->mode != 'w')
                return Z_STREAM_ERROR;

        s->stream.avail_in = 0; /* should be zero already anyway */

        for (;;) {
                len = Z_BUFSIZE - s->stream.avail_out;

                if (len != 0) {
                        if ((uInt)memWrite(s->outbuf, 1, len, s->file) != len) {
                                s->z_err = Z_ERRNO;
                                return Z_ERRNO;
                        }
                        s->stream.next_out = s->outbuf;
                        s->stream.avail_out = Z_BUFSIZE;
                }
                if (done)
                        break;
                s->z_err = deflate(&(s->stream), flush);

                /* Ignore the second of two consecutive flushes: */
                if (len == 0 && s->z_err == Z_BUF_ERROR)
                        s->z_err = Z_OK;

                /* deflate has finished flushing only when it hasn't used up
                 * all the available space in the output buffer:
                 */
                done = (s->stream.avail_out != 0 || s->z_err == Z_STREAM_END);

                if (s->z_err != Z_OK && s->z_err != Z_STREAM_END)
                        break;
        }
        return s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
}

/* ===========================================================================
   Outputs a long in LSB order to the given file
*/
local void putLong(file, x) MEMFILE *file;
uLong x;
{
        int n;
        for (n = 0; n < 4; n++) {
                memPutc((int)(x & 0xff), file);
                x >>= 8;
        }
}

/* ===========================================================================
   Reads a long in LSB order from the given mem_stream. Sets z_err in case
   of error.
*/
local uLong getLong(s) mem_stream *s;
{
        uLong x = (uLong)get_byte(s);
        int c;

        x += ((uLong)get_byte(s)) << 8;
        x += ((uLong)get_byte(s)) << 16;
        c = get_byte(s);
        if (c == EOF)
                s->z_err = Z_DATA_ERROR;
        x += ((uLong)c) << 24;
        return x;
}

/* ===========================================================================
     Flushes all pending output if necessary, closes the compressed file
   and deallocates all the (de)compression state.
*/
int ZEXPORT memgzclose(file) gzFile file;
{
        int err;
        mem_stream *s = (mem_stream *)file;

        if (s == NULL)
                return Z_STREAM_ERROR;

        if (s->mode == 'w') {
#ifdef NO_DEFLATE
                return Z_STREAM_ERROR;
#else
                err = do_flush(file, Z_FINISH);
                if (err != Z_OK)
                        return destroy((mem_stream *)file);

                putLong(s->file, s->crc);
                putLong(s->file, s->stream.total_in);
#endif
        }
        return destroy((mem_stream *)file);
}

long ZEXPORT memtell(file) gzFile file;
{
        mem_stream *s;
        do_flush(file, Z_FULL_FLUSH); // makes memtell to tell truth
        s = (mem_stream *)file;

        if (s == NULL)
                return Z_STREAM_ERROR;

        return memTell(s->file);
}

z_off_t ZEXPORT memgzseek(gzFile file, z_off_t off, int whence)
{
        char buf[80];

        if (whence != SEEK_CUR) {
                fputs("FIXME: memgzio does not support seeking\n", stderr);
                exit(1);
        }

        // this is inefficient, but the best I can do without actually reading
        // the above code
        while (off > 0) {
                int r = memgzread(file, buf, off > 80 ? 80 : off);
                if (r <= 0)
                        return -1;
                off -= r;
        }
        return memtell(file);
}
